1. The Field of the Invention
The present invention relates to gingival retraction cords. More particularly, the invention relates to gingival retraction cords that incorporate propylhexedrine as an improved hemostatic agent and tissue displacing agent, together with optional components, such as one or more astringents or carriers.
2. The Relevant Technology
When performing a variety of dental procedures, it is often desirable to retract gingival tissue in order to prepare a patient""s teeth for, e.g., taking dental impressions, placing crowns, performing bridge work, or effecting other dental restorations. A widely used procedure for retracting gingival tissue involves the use of retraction cords which are typically braided or knitted for increased strength, flexibility and resilience.
Examples of braided or knitted gingival retraction cords maybe found in U.S. Pat. No. 4,321,038 to Porteous, U.S. Pat. No. 4,522,933 to Fischer, U.S. Pat. No. 4,617,950 to Porteous et al., and U.S. Pat. No. 4,892,482 to Lococo.
The most common purpose for using a retraction cord is to retract the gingiva away from the tooth in order to take a more accurate and reliable impression of the tooth being restored. It has been found that in order to construct artificial crowns capable of remaining secured to the tooth in a physiologically sound condition and for an extended period of time, it is critical to make an accurate impression of the tooth, particularly in the area at or below the gingival margin. Failure to take an accurate impression can result in a poorly-formed or deficient prosthesis, particularly at the gingival margin. Premature failure of a crown is often due to poor marginal detail in the impression used to fabricate the crown.
The person""s gingiva, or xe2x80x9cgumsxe2x80x9d, not only prevents an accurate impression of the proper shape of a person""s tooth beneath the gingiva, it may also bleed if torn or damaged by high speed cutting drills or burrs used to remove tooth material preparatory to placing a crown. This bleeding may further interfere with the taking of a good impression because extravasated blood tends to prevent adequate cleaning and drying of the marginal area of the tooth prior to taking an impression and tends to displace the impression material before it can set. Thus, the dual problems of contraction of the gingival cuff and the presence of hemorrhaging tissues make it impractical to simply take an impression following shaping of the tooth with a high speed drill or burr without retraction of the gingiva.
In order to control or inhibit the tendency of the gingiva to bleed when physically retracted by the retraction cord and/or if accidentally cut or nicked by the high speed drill or burr, retraction cords are often treated with a hemostatic agent. One type of hemostatic agent includes astringents, which lock or seal off exposed blood vessels so as to arrest bleeding. U.S. Pat. Nos. 4,321,038, 4,522,933, 4,617,950 and 4,892,482, referred to above, discuss the use of astringents such as xe2x80x9calumxe2x80x9d, or potassium aluminum sulfate.
U.S. Pat. Nos. 4,321,038 and 4,892,402 also discuss the use of epinephrine, which is often used in the form of a salt, typically epinephrine hydrochloride, and which is a known vasoconstrictor. Although epinephrine is commonly used as a vasoconstrictor in a wide variety of applications, the use of epinephrine has the tendency to cause systemic, rather than merely localized, physiological responses. In particular, whereas the topical use of epinephrine may provide a desired hemostatic effect, it is known to produce the side effect of increasing a person""s pulse rate and blood pressure. This is not surprising since epinephrine is the principal sympathomimetic hormone produced by the adrenal medulla. Hence, epinephrine is often referred to as xe2x80x9cadrenalinexe2x80x9d, the xe2x80x9cfight or flightxe2x80x9d hormone, which is associated with fear, excitement, anxiety or other similar emotional and biochemical responses which result in increased pulse rate, elevated blood pressure, and accelerated metabolism. This has in a few cases caused the death of compromised heart heart patients. Nevertheless, it is still commonly used in conventional retraction cords due to the perceived lack of adequate substitutes.
Another drawback of epinephrine is that it is incompatible with the use of iron-based hemostatic agents. In particular, it has been found that epinephrine and ferric iron compounds react to form a purple reaction product. Not only would the reaction of epinephrine and ferric iron-based compounds diminish the activity of both agents, it would also result in a discolored retraction cord which, in turn, would temporarily stain the patient""s teeth and gums, as well as the fingers of the dental practitioner attempting to place a retraction cord that included epinephrine and an iron-based hemostatic agent.
In short, it would be an advancement in the art to provide improved gingival retraction cords capable of providing hemostasis without the drawbacks inherent in the use of epinephrine.
More particularly, it would be an important advancement in the art to provide gingival retraction cords that included a vasoconstricting hemostatic agent which did not result in increased pulse rate and elevated blood pressure of the patient.
It would be a further advancement in the art to provide improved hemostatic retraction cords which employed a vasoconstrictor which allowed for the optional inclusion of a wide variety of astringents, including iron-containing compounds, which did not result in the formation of colored reaction products between the vasoconstrictor and the optional astringent.
For example, it would be an advancement in the art to provide a retraction cord which included a vasoconstrictor in combination with an iron-based hemostatic agent which did not result in discoloration of the retraction cord, the patient""s teeth and gums, or the fingers of the dental practitioner attempting to place the retraction cord.
Such improved gingival retraction cords for providing hemostasis with a minimum of undesired side effects are disclosed and claimed herein.
The present invention relates to improved gingival retraction cords that have been treated with propylhexedrine and optionally astringents and other active agents. The gingival retraction cords of the present invention provide superior hemostatic and gingiva retraction or displacement properties while avoiding the detrimental side effects of vasoconstrictors such as epinephrine. This is because propylhexedrine has been shown to have a much more localized vasoconstricting effect than epinephrine. Moreover, propylhexedrine is not an adrenal hormone like epinephrine and, hence, does not have the same hormonal effect on a person""s biochemistry, pulse and heart rate. By substituting propylhexedrine for epinephrine, it is now possible for the retraction cords according to the present invention to provide superior hemostasis of bleeding gingival tissue by means of a vasoconstrictor having similar vasoconstriction properties compared to epinephrine, but without the systemic side effects of epinephrine, namely, increased heart rate and blood pressure.
The retraction cord may be advantageously xe2x80x9cdopedxe2x80x9d with propylhexedrine by dipping or otherwise soaking the cord in an appropriate solution of propylhexedrine, either alone or in combination with other desired agents. In order to make propylhexedrine more water soluble, it may advantageously be utilized in the form of a salt, such as propylhexedrine hydrochloride. In its salt form, propylhexedrine may be readily dissolved in water or other highly polar solvents such as DMSO, glycerine or alcohol. Propylhexedrine, when not in its salt form, is readily soluble in alcohol, chloroform and ether.
In a preferred embodiment, the retraction cord will include a concentration of propylhexedrine in a range from about 0.01 mg/inch to about 1 mg/inch of the retraction cord, more preferably in a range from about 0.05 mg/inch to about 0.5 mg/inch, and most preferably in a range from about 0.75 mg/inch to about 1.25 mg/inch of the gingival retraction cord.
The desired hemostatic effect of propylhexedrine may be enhanced through the use of one or more auxiliary hemostatic agents such as astringents. A common astringent is alum, which is potassium aluminum sulfate. However, more effective hemostatic agents include a variety of iron compounds, such as ferric sulfate and ferric chloride.
An advantage of propylhexedrine over epinephrine is that propylhexedrine does not react with iron-containing compounds. The result is the ability to derive the full benefit or effect of propylhexedrine and also of iron-containing astringent compounds. Moreover, unlike epinephrine, propylhexedrine does not form colored reaction products with iron-containing compounds. Hence, that retraction cords containing propylhexedrine and iron-containing compounds will not discolor the retraction cord, the patient""s teeth and gums, and the fingers of the dental practitioner as could occur if epinephrine were used with ferric astringent compounds.
Preferred retraction cords are knitted in order to provide a superior balance of strength, longitudinal elongation, and transverse resilience. This provides the most effective cord for withdrawing the gingival cuff while exerting the least pain on the patient and providing the greatest ease of placement for the dental practitioner, as discussed full in U.S. Pat. No. 4,522,593 to Fischer.
Accordingly, it is an object of the invention to provide improved gingival retraction cords capable of providing hemostasis without the drawback inherent in the use of epinephrine.
It is a more particular object of the invention to provide gingival retraction cords that include a hemostatic agent which does not result in increased pulse rate and elevated blood pressure of the patient.
It is a further object and feature of the invention to provide hemostatic retraction cords which employ a vasoconstrictor which allows for the optional inclusion of a wide variety of astringents or other hemostatic agents, including iron-containing compounds, which does not result in the formation of colored reaction products between the vasoconstrictor and the optional hemostatic agent.
In a preferred embodiment, it is an object of the invention to provide a retraction cord which includes a vasoconstrictor in combination with an iron-based astringent hemostatic agent which does not result in discoloration of the retraction cord, the patient""s teeth and gums, and the fingers of the dental practitioner attempting to place the retraction cord.
These and other objects and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.